Carol Elizabeth Moseley was born in Chicago, Illinois, and educated in the Chicago public school system. Her father, Joseph Moseley, was a law enforcement officer and her mother, Edna, was a medical technician. She graduated from the University of Illinois at Chicago in 1969 and earned a Juris Doctor degree from the University of Chicago in 1972.

As an attorney, Moseley Braun was a prosecutor in the United States Attorney's office in Chicago from 1973 to 1977. An Assistant United States Attorney, she worked primarily in the civil and appellate law areas and tried cases of national importance.[citation needed] Her work in housing, health policy, and environmental law won her the Attorney General's Special Achievement Award. She subsequently received over 300 awards for achievements in the public interest.[citation needed]

Moseley Braun was first elected to public office in 1978, as a member of the Illinois House of Representatives. There, she rose to the post of assistant majority leader. As a State Representative, she became recognized as a champion for education, governmental reform, and civil rights.[citation needed] As early as 1984, she proposed a moratorium on the application in Illinois of the death penalty. And in what became a landmark reapportionment case, Crosby vs State Board of Elections, she successfully sued her own party and the state of Illinois on behalf of African American and Hispanic citizens. When she left the state legislature in 1987, her colleagues recognized her in a resolution as "the conscience of the House."[citation needed] That same year, she was elected as Cook County, Illinois, Recorder of Deeds, a post she held for four years.

In 1991, angered by incumbent Democratic senator Alan Dixon's vote to confirm Clarence Thomas, Moseley Braun challenged him in the primary election. Candidate Albert Hofeld's campaign ran many anti-Dixon ads, and Moseley Braun won the primary, ultimately defeating Richard S. Williamson in the Senate election. On November 3, 1992, she became the first African American woman to be elected to the United States Senate. Her election marked the first time Illinois had elected a woman, and the second time a black person was elected as a Democrat to the United States Senate. She (along with Edward Brooke) was one of two African-Americans to serve in the Senate in the 20th century, and was the sole African-American in the Senate for her entire term.

Despite her reputation as a liberal, Moseley Braun possessed something of a centrist record on economic issues. She voted for the 1993 budget package and against the welfare reform laws passed in 1996, but on many other matters she was more conservative. Moseley Braun voted in favor of the North American Free Trade Agreement (NAFTA) and lawsuit reform measures like the Private Securities Litigation Reform Act (she was also among the minority of Democrats to support the even more controversial Common Sense Product Liability and Legal Reform Act of 1995). She also voted contrary to the interests of the more populist wing of the party by voting for the Freedom to Farm Act and the Telecommunications Act of 1996. Like her Illinois colleague, fellow Democrat Paul Simon, she voted in favor of a Balanced Budget Amendment to the United States Constitution and also to place a nuclear dump in Nevada, a move strongly opposed by many Democrats, especially current Majority Leader Harry Reid.

On social issues however, she was significantly more liberal than many of her fellow senators. She was strongly pro-choice, voting against the ban on partial-birth abortions and the restrictions on funding in military bases for abortions. She also voted against the death penalty and in favor of gun control measures. Moseley Braun was one of only sixteen senators to vote against the Communications Decency Act and one of only fourteen to vote against the Defense of Marriage Act. She delivered a eulogy to Thurgood Marshall on January 26, 1993.

Carol Moseley Braun was a one-term Senator, losing to Republican Peter Fitzgerald in her re-election bid in 1998.

Moseley Braun was the subject of a 1993 Federal Elections Commission investigation over $249,000 in unaccounted-for campaign funds. The agency found some small violations, but took no action against Moseley Braun, citing a lack of resources. Moseley Braun only admitted to bookkeeping errors. The Justice Department turned down two requests for investigations from the IRS.

In 1996, Moseley Braun made a private trip to Nigeria, where she met with dictator Sani Abacha. Despite U.S. sanctions against that country, due to Abacha's actions, the Senator did not notify, nor register her trip with, the State Department. She subsequently defended Abacha's human rights records in Congress. Her former fiancé Kgosie Matthews, who also served on her campaign staff (in violation of U.S. immigration regulations), had been a lobbyist for the Nigerian government; Matthews would later leave the country.

In 1998, after George Will wrote a column reviewing the allegations of corruption against her, Moseley Braun responded to Will's comments, saying that "I think because he couldn't say nigger, he said corrupt," She also compared Will to a Ku Klux Klansman, saying "I mean this very sincerely from the bottom of my heart: He can take his hood and put it back on again, as far as I'm concerned." Later, Moseley Braun apologized for her remarks.